Process for preparing 1,2,4-thiadiazole derivatives

ABSTRACT

An improved process for the production of 5-amino-1,2,4-thiadiazol-3-yl-(2-(lower)-alkoxyimino)acetic acids starting from 5-substituted- or unsubstituted-3-aminoisoxazole compounds is disclosed herein. The title compounds are useful as acylating agents for the production of 7-acylaminocephalosporins.

This is a divisional of application Ser. No. 08/225,920 filed on Apr.11, 1994, U.S. Pat. No. 5,585,494, which is a continuation ofapplication Ser. No. 07/941,246, filed Sep. 4, 1992, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to 1,2,4-thiadiazole compounds as well asthe production and a use thereof. Particularly, the present inventionrelates to 1,2,4-thiadiazole compounds utilizable as the startingmaterials for the synthesis of acylating agents which are used in theproduction of 7-acylaminocephalosporins useful as antibiotics as well asa process for their production and a use of them.

2. Background Information

Various 7-acylaminocephalosporins have been known as antibiotics andvarious processes for the production of them have also been reported.Among these processes, most typical one is a process in which7-aminocephalosporins are converted into 7-acylaminocephalosporins bythe action of an acylating agent. A wide variety of acylating agents areproposed for use in this converting process, because antimicrobialactivity of the produced 7-acylaminocephalosporins greatly depends onthe acylating agents. Among the acylating agents,2-(5-amino-1,2,4-thiadiazol-3-yl)acetic acid and its reactivederivatives are widely applied due to the fact that the produced 7-2-(5-amino-1,2,4-thiadiazol-3-yl)acetamido!cephalosporins generally haveexcellent antimicrobial activity.

Although various methods have been known for the production of the above2-(5-amino-1,2,4-thiadiazol-3-yl) acetic acid and its reactivederivatives, all these methods have any drawbacks from the viewpoint ofcommercial production. For example, it is reported that said acid can beproduced by protecting amino group of 5-amino-3-methyl-1,2,4-thiadizole,reacting the product with lithium diisopropylamide prepared fromdiisopropylamine and butyl lithium, and converting methyl group tocarboxymethyl group by introducing carbon dioxide, but this method has afault that butyl lithium should be used at a temperature as low as -78°C. for preparing lithium diisopropylamide.

The present inventors discovered, in the course of research for thedevelopment of commercially advantageous process for the production of2-(5-amino-1,2,4-thiadiazol-3-yl)acetic acid and its reactivederivatives, a novel rearrangement reaction in which isoxazole compoundsare converted into 1,2,4-thiadiazole compounds, said rearrangementreaction leading to a new and commercially advantageous preparationmethod, comprising a series of reaction steps, for the production of2-(5-amino-1,2,4-thiadiazol-3-yl)acetic acid and its reactivederivatives. The present invention provides a step of producing loweralkyl 2-(5-substituted-amino-1,2,4-thiadiazol-3-yl)acetate by therearrangement of 3-amino-5-lower alkoxy isoxazole, said step being thekey step in the series of steps for the production. The presentinvention also provides a step of producing lower alkyl2-(5-substituted-amino-1,2,4-thiadiazol-3-yl)-2-oxoacetate in acommercially advantageous manner by oxidizing lower alkyl2-(5-substituted-amino-1,2,4-thiadiazol-3-yl)acetate. The presentinvention further provides a process for the production of2-(5-amino-1,2,4-thiadiazol-3-yl)acetic acid and its reactive derivativewhich comprises a series of steps including said key step.

SUMMARY OF THE INVENTION

The present invention provides the following processes and products.

(1) A process for the production of5-amino-1,2,4-thiadiazol-3-yl-(2-(lower)alkoxyimino)acetic acid compoundwhich comprises

a) reacting an isoxazole of the formula: ##STR1## wherein R¹ is loweralkyl, with either a thiocyanate and an acyl halide or a reactionproduct of them to give a 1,2,4-thiadiazolylacetic acid compound of theformula: ##STR2## wherein R¹ is as defined above, and R² is optionallysubstituted lower alkyl, optionally substituted phenyl, optionallysubstituted phenyl(lower) alkyl, optionally substituted lower alkoxy,optionally substituted phenoxy or optionallysubstituted-phenyl(lower)alkyloxy, or

b) i) reacting 3-aminoisoxazole with either a thiocyanate and an acylhalide or a reaction product of them to give an isoxazolylthiourea ofthe formula: ##STR3## wherein R² is defined above, ii) subjecting thecompound (III) to rearrangement reaction to give a1,2,4-thiadiazolylacetaldehyde of the formula: ##STR4## wherein R² is asdefined above, or acetal or hemiacetal thereof, iii) oxidizing thecompound (IV) obtained in (ii) to give a 1,2,4-thiadiazolylacetic acidof the formula: ##STR5## wherein R² is as defined above, and iv)esterifying the compound (V) to give lower alkyl1,2,4-thiadiazolylacetate of the formula (II), or

c) i) oxidizing the compound of the formula (II) with dimethylsulfoxide, iodine and sulfuric acid to give a1,2,4-thiadiazolyl-(2-oxo)acetate compound of the formula: ##STR6##wherein R¹ and R² are as defined above, ii) reacting the compound (VI)with an N-(lower)alkoxyamine to give a1,2,4-thiadiazolyl-(2-(lower)alkoxyimino)acetate compound of theformula: ##STR7## wherein R¹ and R² are as defined above, and R³ islower alkyl, halo(lower)alkyl, carboxy(lower)alkyl or(lower)alkoxycarbonyl(lower)alkyl, and

iii) optionally hydrolyzing the compound (VII) to give a1,2,4-thiadiazolyl-(2-(lower)alkoxyimino)acetic acid compound of theformula: ##STR8## wherein R² and R³ are as defined above, or d) i)reacting a syn-isomer of 1,2,4-thiadiazolacetic acid compound of theformula: ##STR9## wherein R⁴ is carboxy-protecting group and R⁵ isamino-protecting group, with a nitrous acid ester to give a syn-isomerof 1,2,4-thiadiazol-(2-hydroxyimino)acetic acid compound of the formula:##STR10## wherein R⁴ and R⁵ are as defined above, ii) reacting thecompound (X) with

iia) a compound of the formula:

    R.sup.3 --X                                                (XI)

wherein R³ is lower alkyl, halo(lower)alkyl, carboxy(lower)alkyl or(lower)alkoxycarbonyl(lower)alkyl, and X is halogen atom, in thepresence of silver oxide, or

iib) a compound of the formula:

    R.sup.3 --Y                                                (XII)

wherein R³ is as defined above and Y is acid residue,

in the presence of barium oxide and barium hydroxide, to give asyn-isomer of 1,2,4-thiadiazolyl-(2-substituted-oxyimino)acetic acidcompound of the formula: ##STR11## wherein R³, R⁴ and R⁵ are as definedabove, and optionally subjecting the compound (XIII) to eliminationreaction of protecting group(s).

(2) A process for the production of 1,2,4-thiadiazolylacetic acidcompound which comprises reacting an isoxazole of the formula: ##STR12##wherein R¹ is lower alkyl, with either a thiocyanate and an acyl halideor a reaction product of them to give a 1,2,4-thiadiazolylacetic acidcompound of the formula: ##STR13## wherein R¹ is lower alkyl, and R² isoptionally substituted lower alkyl, optionally substituted phenyl oroptionally substituted phenyl(lower) alkyl, optionally substituted loweralkoxy, optionally substituted phenoxy or optionally substitutedphenyl(lower)alkoxy.

(3) A process for the production of 1,2,4-thiadiazol-3-yl-(2-oxo)-aceticacid compound which comprises oxidizing the compound of the formula(II): ##STR14## wherein R¹ is lower alkyl, and R² is optionallysubstituted lower alkyl, optionally substituted phenyl or optionallysubstituted phenyl(lower) alkyl, optionally substituted lower alkoxy,optionally substituted phenoxy or optionally substitutedphenyl(lower)alkyloxy, with dimethyl sulfoxide, iodine and sulfuric acidto give a 1,2,4-thiadiazolyl-(2-oxo)acetate compound of the formula:##STR15## wherein R¹ and R² are as defined above.

(4) A process for the production of5-amino-1,2,4-thiadiazol-3-yl-(2-(lower)alkoxyimino)acetic acid compoundwhich comprises

i) reacting an isoxazole of the formula: ##STR16## wherein R¹ is loweralkyl, with a thiocyanate and a haloformate or a reaction product ofthem to give a 1,2,4-thiadiazolylacetic acid compound of the formula:##STR17## wherein R¹ is lower alkyl, and R² is optionally substitutedlower alkyl, optionally substituted phenyl or optionally substitutedphenyl(lower) alkyl, optionally substituted lower alkoxy, optionallysubstituted phenoxy or optionally substituted phenyl(lower)alkyloxy, and

ii) oxidizing the compound of the formula (II) to give a1,2,4-thiadiazolyl-(2-oxo)acetate compound of the formula: ##STR18##wherein R¹ and R² are as defined above, iii) reacting the compound (VI)with an N-(lower)alkoxyamine to give a1,2,4-thiadiazolyl-(2-(lower)alkoxyimino)acetate compound of theformula: ##STR19## wherein R¹ and R² are as defined above, and R³ islower alkyl, halo(lower)alkyl, carboxy(lower)alkyl or(lower)alkoxycarbonyl(lower)alkyl, and

iv) optionally hydrolyzing the compound (VII) to give a1,2,4-thiadiazolyl-(2-(lower)alkoxyimino)acetic acid compound of theformula: ##STR20## wherein R³ are as defined above.

(5) A process for the production of 1,2,4-thiadiazolylacetic acidcompound which comprises reacting 3-aminoisoxazole with either athiocyanate and an acyl halide or a reaction product of them to give anisoxazolylthiourea of the formula: ##STR21## wherein R² is optionallysubstituted lower alkyl, optionally substituted phenyl or optionallysubstituted phenyl(lower) alkyl, optionally substituted lower alkoxy,optionally substituted phenoxy or optionally substitutedphenyl(lower)alkyloxy,

ii) subjecting the compound (III) to rearrangement reaction to give a1,2,4-thiadiazolylacetaldehyde of the formula: ##STR22## wherein R² isas defined above, or acetal or hemiacetal thereof, iii) oxidizing thecompound (IV) obtained in (ii) to give a 1,2,4-thiadiazolylacetic acidof the formula: ##STR23## wherein R² is as defined above, and iv)optionally esterifying the compound (V) to give lower alkyl1,2,4-thiadiazolylacetate of the formula (II).

(6) An isoxazolylthiourea of the formula: ##STR24## wherein R² isoptionally substituted lower alkyl, optionally substituted phenyl oroptionally substituted phenyl(lower) alkyl, optionally substituted loweralkoxy, optionally substituted phenoxy or optionally substitutedphenyl(lower)alkyloxy.

(7) A 1,2,4-thiadiazolylacetaldehyde of the formula: ##STR25## whereinR² is optionally substituted lower alkyl, optionally substituted phenylor optionally substituted phenyl(lower) alkyl, optionally substitutedlower alkoxy, optionally substituted phenoxy or optionally substitutedphenyl(lower)alkyloxy.

(8) A process for the production of5-amino-1,2,4-thiadiazol-3-yl-(2-(lower)alkoxyimino)acetic acid compoundwhich comprises

i) reacting a syn-isomer of the compound (X) of the formula: ##STR26##wherein R⁴ is carboxy-protecting group and R⁵ is amino-protecting group,with iia) a compound of the formula:

    R.sup.3 --X                                                XI

wherein R³ is lower alkyl, halo(lower)alkyl, carboxy(lower)alkyl or(lower)alkoxycarbonyl(lower)alkyl, and X is halogen atom, in thepresence of silver oxide, or

iib) a compound of the formula:

    R.sup.3 --Y                                                XII

wherein R³ is as defined above and Y is acid residue,

in the presence of barium oxide and barium hydroxide, to give asyn-isomer of 1,2,4-thiadiazol-(2-substituted-oxyimino)acetic acidcompound of the formula: ##STR27## wherein R³ R⁴ and R⁵ are as definedabove and optionally subjecting the compound (XIII) to eliminationreaction of protecting group(s) to give an5-amino-1,2,4-thiadiazol-3-yl-(2-(lower)alkoxyimino)acetic acid compoundof the formula: ##STR28## wherein R³ is as defined above.

(9) A process for the production of5-amino-1,2,4-thiadiazol-3-yl-(2-hydroxyimino)acetic acid compound whichcomprises reacting a 1,2,4-thiadiazolacetic acid compound of theformula: ##STR29## wherein R⁴ is a carboxy-protecting group and R⁵ isamino-protecting group, with a nitrous acid ester to give a1,2,4-thiadiazol-(2-hydroxyimino)acetic acid compound of the formula:##STR30## wherein R⁴ and R⁵ are as defined above.

DETAILED DESCRIPTION OF THE INVENTION

The terms and definitions described in this specification areillustrated as follows:

Only for the convenient sake, the partial structure of the formula:##STR31## includes both of the geometric structures "syn" and "anti"unless otherwise specified. The "syn"-isomer as described in thisspecification is intended to mean the isomer having the geometricstructure in which --o-- bonded to N and --COO-- bonded to C are on thesame side in relation to the C═N double bond, regardless to the abovedefinition of the partial structure.

The thiadiazolyl group is well known to lie in tautomeric relation witha thiadiazolinyl group. Accordingly, it is to be understood that both ofthe said groups are substantially the same, and the tautomers consistingof such groups are regarded as the same compounds especially in themanufacturing chemistry. Therefore, both of the tautomeric forms of thecompounds having such groups in their molecule are included in the scopeof this invention and designated inclusively with one expression"thiadiazolyl" only for the convenient sake throughout thisspecification.

The term "lower" is intended to include a group having 1 to 6 carbonatoms unless otherwise specified.

Therefore, the term "lower alkyl" as a group or a moiety ofphenyl(lower)alkyl, carboxy(lower)alkyl or halo(lower)alkyl includesaturated and straight or branched chain hydrocarbon radicals containing1 to 6, preferably 1 to 5 and more preferable 1 to 4 carbon atoms, suchas methyl, ethyl, propyl, isopropyl, butyl, t-butyl, pentyl, hexyl.

The term "phenyl(lower)alkyl" includes, for example, benzyl phenethyl,etc.

The word "substituted" means that any group can be present on loweralkyl, phenyl, phenyl(lower) alkyl, lower alkyloxy, phenyloxy andpheny(lower)alkyloxy groups, and such a group may be any one that doesnot have adverse effect on the reaction of the present invention, andchosen from lower alkyl, lower alkoxy, hydroxy, halogen and nitro.

The term "halo(lower)alkyl" refers to a lower alkyl group as definedabove which is substituted with at least one and preferably 1 to 3halogen atoms and includes for example, chloromethyl, bromomethyl,fluoromethyl, trifluoromethyl, 1,2-dichloromethyl,1,2,2-trichloromethyl, chloroporpyl, chlorobutyl, chloropentyl,chlorohexyl etc.

The term "carboxy(lower)alkyl" refers to a lower alkyl as defined abovewhich is substituted with at least one carboxy group, such ascarboxymethyl, 1-carboxyethyl, 2-carboxyethyl and1-methyl-1-carboxyethyl.

The term "lower alkoxycarbonyl" is represented by the formula:R--O--CO--R-- wherein R is a lower alkyl defined above and R' is a loweralkylene obtainable by removing a hydrogen atom from the lower alkylgroup as defined above.

The term "optionally" means that the subsequently described event orcircumstance may not occur, and that the description includes instanceswhere said event or circumstance occurs and instances in which it doesnot. For example, "optionally substituted phenyl" means that the phenylmay or may not be substituted and that the description includes bothunsubstituted phenyl and phenyl wherein there is substitution.

The term "halogen" includes chlorine, bromine, iodine and fluorine.

The term "carboxy-protecting group" and "amino-protecting group" havethe meanings used in peptide synthesis.

The typical carboxy protecting groups together with the eliminatingmethod thereof are described, for example, in "Shinjikkenkagakukoza" 14,2535-2544 and Peptide Synthesis (Second Edition, M. Bodansky. Y. S.Klausner and M. A. Ondetti, John Wily & Sons, 1976), Chapter 4, andthere are included, for example, lower alkyl, such as methyl (removableby acid or alkali), ethyl (the same as methyl) and t-butyl (removable byHCl/CH₂ Cl₂, CH₃ COOH, TsOH/ACOH, etc), halo(lower)alkyl, such as2,2,2-trichloroethyl (removable by Zn/AcOH and HCOOH, etc),loweralkylthio(lower)alkyl, such as methylthioethyl (removable by CH₃ Iand then alkali), lower alkoxy(lower)alkyl, such as methoxymethyl(removable by acid), arylsulfonyl(lower)alkyl, such as tosylethyl(removable by NaOH/dioxane), optionally substitutedarylthio(lower)alkyl, such as p-nitrophenylthio (removable by alkaliafter oxydizing to a sulfone), aryl(lower)alkyl, such as benzyl(removable by H₂ /Pd, Na/NH₃, NaOH/dioxane, HBr/AcOH, etc),p-methoxybenzyl (removable by H₂ /Pd, CF₃ COOH, HCOOH, etc),2,4,6-trimethoxybenzyl (removable by HBr/AcOH), pentamethlbenzyl(removable by CF₃ COOH), p-nitrobenzyl (removable by H₂ /Pd, NaOH),benzhydryl (removable by H₂ /Pd, NaOH), trityl (removable by NaOH,HCl/CH₃ OH), anthranylmethyl (removable by HBr/AcOH, NaOH, CF₃ COOH) andhydroxamic acid (removable by HIO₄).

The typical amino-protecting groups together with the eliminating methodthereof is described, for example, in "Shinjikkenkagakukoza" 14,2555-2569 and "Peptide Synthesis" (The Second Edition, M. Bodansky. Y.S. Klausner and M. A. Ondetti, John Wily & Sons, 1976), Chapter 4, thereare included, for example; as a acyl type, lower alkanoyl, such asformyl (removable by HCl/CH₃ OH), acetyl (removable by acid or alkali),halo(lower)alkanoyl, such as 2-chloropropionyl (removable by acid oralkali), arylcarbonyl, such as benzoyl (removable by acid or alkali),aryl(lower)alkanoyl, such as phenylpropionyl (removable by acid oralkali); as a urethane type, lower alkoxycarbonyl, such asmethoxycarbonyl, ethoxycarbonyl, t-buthoxycarbonyl (removable by HBr orHCl/AcOH), aryl(lower)alkoxycarbonyl, such as benzyloxycarbonyl(removable by H₂ /Pd, HI or HBr/AcOH, etc),2-(p-biphenyl)isopropoxycarbonyl (removable by AcOH/HCOOH,trifluoroacetic acid, etc); as a aralkyl type, aryl(lower)aralkyl, suchas benzyl (removable by H₂ /Pd, Na/NH₃), trityl (removable by H₂ /Pd);and as an azomethine type, aryl(lower)alkylidene, such as benzylidene(removable by H₂ /Pd, HCl).

In the above mentioned groups, "aryl" group includes a group having oneto three bezene rings.

Since "carboxy-protecting group" or "amino-protecting group" definedabove is finally to be eliminated, selection of the group is notimportant.

The term "acid residue" includes sulfur acid such as sulfuric acid,organosulfonic acid (e.g. lower alkyl sulfonic acid, such as methanesulfonic acid, ethane sulfonic acid and aryl sulfonic acid, such asbenzene sulfonic acid, toluene sulfonic acid), and organocarboxylicacid, such as tartaric acid.

The above series of the process steps from an isoxazole compound (I) toa 1,2,4-thiadiazol-3-yl-(2-(lower)alkoxyimino)acetic acid of the formula(VIII), via 1,2,4-thiadiazol-3-yl acetic acid are illustrated below inorder.

In the first step of the present invention, isoxazol (I) is reacted witha thiocyanate and acyl halide or reaction product of them to give a1,2,4-thiadiazolylacetic acid compound (II).

The starting substance, i.e. isoxazole can be prepared by reacting,-dialkoxyacrylonitrile with hydroxylamine as described in JapanesePatent Publication B No. 45-39702.

Thiocyanate as the reacting reagent is preferably alkaline metalthiocyanate (e.g. sodium thiocyanate, potassium thiocyanate), and anacyl halide is preferably a compound of the formula: R² COX wherein R²is as defined above and X is a halogen atom, specifically, lower alkylhaloformate, phenylhaloformate, phenyl(lower)alkyl haloformate,phenylalkyl carbonyl halide, benzoyl halide andphenyl(lower)alkylcarbonyl halide which may be substituted. Isoxazolemay be reacted with thiocyanate and acyl halide, however usuallythiocyanate is previously reacted with acyl halide to prepareacylisothiocyanate, which, after separation or without separation, whichis advantageously reacted with isoxazole. The reaction with thiocyanateand acyl halide or the reaction with acylisothiocyanate is preferablycarried out in a inert solvent, particularly in a polar solvent, such asacetonitrile, dimethylformamide, tetrahydrofuran, etc.

The term "reaction product" includes not only the direct productsproduced by the reaction of thiocyanate and acyl halide but also thecompounds having the same structure but produced by the reaction ofother compounds. Normally, the products have the structure ofacylisothiocyanate.

The typical process is illustrated below: methyl chloroformate isreacted with potassium thiocyanate by heating in acetonitrile, followedby cooling and then 3-amino-methoxy isooxazole is added thereto to reactat room temperature. The reaction mixture is poured onto ice water togive the precipitates of methyl2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate, which areseparated. In the case where the product is not crystallized such asmethyl 2-(5-benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate, thisis extracted with a solvent such as ethyl acetate in order to separate.If necessary, it is possible to purify by sillica gel chromatography.

As the typical compounds of a 1,2,4-thiadiazolyl acetic acid compound(II), there may be mentioned2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetic acid,2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetic acid, methyl2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate, methyl2-(5-phenoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate, methyl2-(5-benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate, methyl2-(5-phenylcarbonylamino-1,2,4-thiadiazol-3-yl)acetate, ethyl2-(5-phenylcarbonylamino-1,2,4-thiadiazol-3-yl)acetate, methyl2-(5-t-butylcarbonylamino-1,2,4-thiadiazol-3-yl)acetate and ethyl2-(5-(4-nitrobenzoyl)carbonylamino-1,2,4-thiadiazol-3-yl)acetate.

In the second step, the obtained 1,2,4-thiadiazolylacetic acid compound(II) is oxidized to give 1,2,4-thiadiazolyl-2-oxo-acetic acid compound(VI).

The oxidation is carried according to a known method, for example, usingselenium dioxide, which is not adapted in a industrial scale productionbecause of its high toxicity. As the result of the intensive study ofvarious oxidizing agent, it has been found that oxidation reaction isadvantageously effected using dimethyl sulfoxide, iodine and sulfuricacid which does not have the toxicity such as that of selenium dioxide.Therefore, dimethyl sulfoxide, iodine and sulfuric acid are particularlypreferred as the oxidizing agent. The amounts of these oxidizing agentsare 3-30 equivalent weight, preferably 5-15 equivalent of dimenthylsulfoxide, 0.05-10 equivalent of iodine, preferably 0.1 equivalent, and0.05-1 equivalent of sulfuric acid, preferably 0.1 equivalent withrespect to 1,2,4-thiadiazolyl acetic acid (II), respectively. Theoxidation reaction is smoothly carried out under heating at 80°-100° C.The reaction solvent is not necessarily used, but when used, it may bechosen from ethyl acetate, benzene, toluene and acetone.

In the third step, 1,2,4-thiadiazolyl-2-oxoacetic acid (IV) is reactedwith a lower alkoxy amine to give 1,2,4-thiadiazolyl-2-(lower)alkoximinoacetic acid (VII).

The lower alkoxy amine is represented by the formula: R³ ONH₂ wherein R³is as defined above, and the typical examples are methoxyamine,ethoxyamine, propoxyamine, etc. In general, the reaction isadvantageously carried out at the temperature of 5°-40° C. On thereaction, the presence of an acid substance, such as hydrochloric acidis preferred as a catalyst. The reaction solvent is not necessarilyused, but when used, it may be appropriately chosen from methanol,ethanol, etc.

In the fourth step, ester moiety is eliminated from the acetic estergroup at the position 3 on1,2,4-thiadiazol-3-yl-2-(lower)alkoxyimino)acetate (VII), or thesubstituted carbonyl group is eliminated from the substitutedcarbonylamino group at the position 5. These eliminations are effectedby heating in the presence of a basic substance (such as sodiumhydroxide). In general, as a temperature, 30°-100° C. is usuallypreferred. If the kind of the basic substance or the heating temperatureis appropriately chosen, the both eliminations of ester moiety at theposition 3 and substituted carbonyl moiety at the position 5 can beeffected simultaneously or succesively to give5-amino-1,2,4-thiadiazol-3-yl-(2-(lower)alkoxyimino)acetic acid compound(VIII). The elimination is usually carried out in an aqueous medium.

It has now been found that the compound (VII) is hydrolized in goodyield to the compound (VIII) via5-acylamino-1,2,4-thiadiazol-3-yl-(2-(lower)alkoxyimino)acetic acidcompound of the formula (XIV): ##STR32## wherein R² is lower alkoxy oroptionally substituted alkyl or optionally substituted aryl. The presentprocess comprises hydolyzing the acetic ester group of the compound(VII) wherein R² is optionally substituted alkyl or optionallysubstituted phenyl with alkali such as alkali metal hydroxides (forexample, NaOH, KOH, etc) to obtain the compound (XIV) and thenhydrolyzing it to the compound (VIII) with aqueous ammonia or organicamines, for example, primary amine such as methylamine, ethylamine,butyl amine, cyclohexylamine, etc or secondary amine, such asdimethylamine, diethanolamine, etc.

The reaction products in the above described steps optionally may beseparated and further purified, or may be applied as such to a next stepwithout purification. The compound (VIII) may be used as an acylatingagent for the production of 7-acylaminosephalosporins according toconventional methods.

The alternative process from 3-aminoisoxazole to 1,2,4-thiadiazolylacetaldehyde (IV) or acetal or hemiacetal thereof is described below.

In the first step, 3-aminoisoxazole is reacted with a thiocyanate andacyl halide or reaction product of them to give an isoxazolylthiourea(III), which is subjected to rearrangement reaction to give1,2,4-thiadiazolyl acetaldehyde (IV) or acetal or hemiacetal thereof.

The starting substance, i.e. 3-aminoisoxazole can be prepared by a knownmethod which, for example, is described in Japanese Patent Publication ANo. 59-128378 which comprises reacting 2-alkoxyacrylonitrile withhydroxylamine, and 3-aminoisoxazole is also available commercially andrelatively at a low price.

The step from 3-aminoisoxazole to isoxazolylythiourea (III) is carriedas described in the above mentioned step, for example, methylchloroformate and potassium thiocyanate is reacted at 40° C.-80° C. for0.5-6 hours in acetonitrile, followed by cooling and 3-aminoisoxazole(I) is added thereto. The resultant mixture is kept at 0°-10° C. for0.5-4 hours in order to complete the reaction. The reaction mixture ispoured onto ice water to give1-(isoxazol-3-yl)-3-methoxycarbonylthiourea, which is filtered off. Ifthe reaction product is not easily crystallized, it may be extracted bya solvent such as ethyl acetate. The product may be applied as such tothe next step without separation.

In the second step, isoxazolylthiourea (III) is subjected torearrangement reaction to give a 1,2,4-thiadiazolylacetaldehyde, acetalor hemiacetal thereof. This reaction is effected by heating at atemperature of which may be usually 20°-100° C., and optionally in thepresence of an inert solvent such as methanol, ethanol, ethyl acetate,etc.

For example, 1-(isoxazol-3-yl)-3-methoxycarbonylthiourea is heated inmethanol at 20°-60° C. for 0.5-4 hours to give precipitates,2-(3-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetaldehyde (IV) oracetal or hemiacetal, which is filtered off.

As described above, since the rearrangement reaction in the first stepis easily effected only by heating, when the temperature of heating isappropriately chosen in the second step, the reactions of the both stepscan be at least partially effected successively to give a mixture ofisoxazolylthiourea (III) and thiadiazolylacetaldehyde (IV).

In the third step, thiadiazolylacetaldehyde (IV) is oxidized to givethiadiazolylacetic acid (V). The oxidization is effected by using anoxidizing reagent, such as silver oxide, chromate, permanganate,hydrogen peroxide, peracid, etc. especially peracetic acid. On theoxidation reaction, it is preferred to use an inert solvent, as atypical example, such as water, t-butanol, methylene chloride, aceticacid, etc. The reaction temperature is usually between 20°-60° C.

For example,2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetaldehyde isdissolved into a mixture of t-butanol and water, and 39% solution ofperacid in acetic acid was added in dropwise thereto, then the resultantmixture is reacted overnight at a room temperature. After decompositionof excess peracid, the precipitated formed is filtered off to give2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetic acid.

Thiadiazolylacetic acid (V) according to the present invention isesterified by a conventional method and oxidized to convert thecorresponding 1,2,4-thiadiazol-3-yl-2-oxoacetic acid ester (VI), thenwhich is reacted with N-(lower)alkoxyamine to give the corresponding1,2,4-thiadiazol-3-yl-2-(lower)alkoxyiminoacetic acid ester (VII). Theobtained compound is optionally hydrolized to give1,2,4-thiadiazol-3-yl-2-(lower)alkoxyimino-acetic acid (VIII) which isuseful for a acylating reagent of the production of 7-acylaminosepharosporin.

Further alternative process from syn-isomer of 1,2,4-thiadiazolylaceticacid compound (IX) to 1,2,4-thiadiazol-3-yl-(2-(lower)alkoxyimino)aceticacid compound (VIII) is described below.

In the first step, a syn-isomer of 1,2,4-thiadiazolylacetic acidcompound (IX) is reacted with a nitrous acid ester to give a syn-isomerof 1,2,4-thiadiazolyl-(2-hydroxyimino)acetic acid compound (X).

Some of the starting substances, i.e. the compound (IX) can be preparedby the process as described in the Journal of Antibiotics, 36,1020-1033, and the others can also be prepared in a similar process. Thecompounds (IX) can also be obtained by new method developed by theinventor of this invention, wherein lower alkoxyisoxazole is reactedwith a thiocyanate and a haloformate.

As "nitrous acid ester", any ester can be used, but in view ofavailability and economy, lower alkoxy nitrite, such as methyl nitrite,ethyl nitrite, butyl nitrite are usually used. Since the ester group iseliminated, kind of the group is not important.

This reaction is effected in the presence of a catalyst. As thecatalyst, an acid such as hydrochloric acid, sulfuric acid, etc or asalt such as lithium chloride are used. The amount of the catalyst isusually 0.1-2 equivalent weight, preferably 0.1-0.2 equivalent. Thereaction is carried out in a solvent, such as tetrahydrofuran, ether,dimethylformamide, methanol, ethanol, buthanol, etc. The reactionproceeds at a room temperature, and is promoted by heating. The reactionproduct is in the form of a syn-isomer and can be separated by aconventional method in which, for example, the reaction solution iswashed, concentrated to give the compound (X).

In the second step, a syn-isomer of the compound (X) is reacted with (a)R³ --X (XI) in the presence of silver oxide or (b) R--Y (XII) in thepresence of barium oxide and barium hydroxide to give1,2,4-thiadiazol-(2-substituted oxyimino)acetic acid compound (XIII),optionally from which amino-protecting group and/or carboxy protectinggroup are eliminated.

As the compound (XI), methyl iodide, ethyl iodide, ethyl bromoacetate,ethyl 2-methyl-2-bromopropionate, chloromethylfluoride, etc and dimethylsulfate, diethyl sulfate may be used.

The reaction using the-compound (XI) or (XII) is effected in a solvent,such as chloroform, acetone, etc and well at a room temperature. Whilethe alkylation in the presence of a basic catalyst is known, accordingto the present inventors, it has been now founded that the alkylation ofthe compound (X) by the combinations of potassium carbonate and thecompound (XI), calcium oxide and the compound (XI), calcium oxide orcalcium hydroxyde and the compound (XII), a mixture of calcium oxide andcalcium hydroxide, barium oxide and the compound (XII), barium hydroxideand the compound (XII) give always (E)-isomer and only the alkylation bythe combination of the present invention gives (Z)-isomer. Theelimination reaction of the protecting group is carried out, forexample, by the method described above for the protecting groups, underthe conditions which are employed for the elimination of the protectinggroups in the peptide synthesis. The protecting groups of R⁴ and R⁵ maybe eliminated separately or simultaneously or succesively. The reactiontemperature is usually about room temperature. In the present reaction,starting from the compound (XIII) wherein R³ is lower alkoxycarbonyl(lower)alkyl, there may be obtained the compound (V) wherein R³carboxy(lower)alkyl, and such a process is also included in the scope ofthe present invention.

The obtained compound (VIII) can be separated by a conventional method,for example, in which the reaction product is washed, extracted,concentrated, and optionally purified by recrystallization or silica gelchromatography to give the compound (VIII). The compounds obtained bythe present invention are useful for a acylating reagent for theproduction of 7-acylaminosephalosporin antibiotics.

The following non-limiting examples illustrate the preparation of thecompounds according to the present invention.

REFERENCE EXAMPLE 1

To a solution of malononitrile (12.0 g; 182 mmol) and methanol (7.35 ml;182 mmol) in anhydrous ether (240 ml) was bubbled hydrogen chloride gas(8.5 g; 0.23 mol) over 1 hour under stirring at -5° C. After thereaction mixture was stirred at the same temperature for 1 hour and thenat room temperature for 6 hours, white crystals formed were filteredoff, washed with ether (100 ml×3) and dried under reduced pressure togive methyl cyanoacetimidate hydrochloride (23.8 g; yield 97.3%).

A suspension of methyl cyanoacetimidate hydrochloride (23.8 g; 177 mmol)in methanol (177 ml) was stirred at room temperature for 12 hours andthen the reaction mixture was directly concentrated. The obtainedresidue was diluted by ethyl acetate (100 ml), washed with saturatedsodium bicarbonate solution and saturated aqueous sodium chloridesolution, dried over sodium sulfate and then concentrated. The crudesyrup obtained was purified by distillation under reduced pressure togive 3,3,3-trimethoxypropanenitrile (bp:110°-112° C./19 mmHg:22.1 g;yield 86.0%).

NMR δ(CDCl₃): 2.87(2H,s,CH₃), 3.36(9H,s,CH₃ ×3)

3,3,3-Trimethoxypropanenitrile (22.1 g; 153 mmol) was stirred at222°-225° C. for 7 minutes. This reaction mixture was purified bydistillation under reduced pressure to give 3,3-dimethoxyacrylonitrile(bp:112° C.-115° C./19 mmHg:13.6 g; yield 3 step 66.1%).

NMR δ(CDCl₃): 3.50(1H,s,H-2), 3.74(3H,s,CH₃) 3.80(3H,s,CH₃)

(B) To a solution of hydroxylamine hydrochloride (1.55 g, 22.3 mmol) inwater (3.41 ml) was added 8N aqueous sodium hydroxide solution (3.35 ml;26.8 mmol) under stirring at room temperature. The temperature waselevated to 45° C. and a solution of 3,3-dimethoxyacrylonitrile (2.27 g;20.1 mmol) in methanol (5.50 ml) was added dropwise for 30 minutes andthen the mixture was stirred at the same temperature for 1 hour. Afterdisappear of 3,3-dimethoxyacrylonitrile was apparent, 8N sodiumhydroxide (1.25 ml; 10.1 mmol) was added to the mixture at the sametemperature and the temperature was elevated to 60° C. The mixture wasstirred for 6 hours. After the reaction was completed, the reactionmixture was directly concentrated (60° C./19 mmHg: until an inorganiccompound was begun to precipitate). The obtained concentrate wasextracted with ethyl acetate (5 ml×3) and the extract was dried oversodium sulfate and concentrated and the residue was dried under reducedpressure to give 3-amino-5-methoxyisoxazole (1.63 g; yield 70.6%) aswhite crystals.

m.p. 82°-83° C. (hexane-ethyl acetate)

NMR δ(CDCl₃): 3.93(5H,bs,CH₃ +NH₂), 4.81(1H,s,H-4)

NMR δ(CDCl₃ +D₂ O): 3.93 (3H,s,CH₃), 4.83(1H,s,H-4)

IR(CHL₃)cm⁻¹ : 3840, 1628, 1487.

Anal. Calcd. for C₄ H₆ N₂ O₂ : C,42.11; H,5.30; N, 24.55(%). Found:C,41.74; H, 5.06; N, 24.35(%).

EXAMPLE 1

A suspension of methyl chloroformate (167 μl; 2.16 mmol) and potassiumthiocyanate (227 mg; 2.34 mmol) in acetonitrile (1.80 ml) was stirred at70° C. for 30 minutes, and then 3-amino-5-methoxyisoxazole (205 mg; 1.80mmol) was added to the suspension under stirring and ice-cooling. Afterstirring for 10 minutes at the same temperature and then for 15 minutesat room temperature, the reaction mixture was poured into ice-water (18ml). The precipitates formed were filtered off, washed with water, thenwith ether and dried under reduced pressure to give methyl2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate (334 mg, yield80.6%).

m.p. 167°-169° C.(MeOH)

NMR δ(CDCl₃): 3.73 (3H. s. COOCH₃) 3.95 (3H. s. NHCOOCH₃) 3.97 (2H. s.CH₂) 10.50(1H. bs. NH)

IR (CHCL₃)cm⁻¹ : 3406. 1736. 1549.

Anal. Calcd. for C₇ H₉ N₃ O₄ S: C,36.36;H,3.92;N,18.17(%). Found:C,36.40;H,3.94;N,18.11(%).

EXAMPLE 2

A suspension of ethyl chloroformate (124 μl; 1.29 mmol) and potassiumthiocyanate (136 mg; 1.40 mmol) in acetonitrile (1.08 ml) was treatedwith 3-amino-5-methoxyisoxazole (123 mg; 1.08 mmol) in the same manneras in Example 1 except that ethyl chloroformate was substituted formethyl chloroformate to give methyl2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate (209 mg; yield78.9%).

m.p. 110°-112° C.(MeOH)

NMR δ(CDCl₃): 1.38(3H.t.CH₃) 3.73(3H.s.COOCH₃) 3.97(2H.s.CH₂ COOCH₃)4.39(2H.q.CH₂) 10.45(1H.bs.NH)

IR(CHCl₃)cm⁻¹ : 3406, 1732, 1564.

Anal. Calcd. for C₈ H₁₁ N₃ O₄ S: C,39.18;H,4.52;N,17.13(%). Found:C,39.16;H,4.40;N,17.18(%).

EXAMPLE 3

A suspension of phenyl chloroformate (232 μl; 1.85 mmol) and potassiumthiocyanate (195 mg; 2.00 mmol) in acetonitrile (1.54 ml) was treatedwith 3-amino-5-methoxyisoxazole (170 mg; 1.49 mmol) in the same manneras in Example 1 except that phenyl chloroformate was substituted formethyl chloroformate to give methyl2-(5-phenoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate (251 mg; yield57.4%).

m.p. 162°-164° C.(MeOH)

NMR δ(CDCl₃): 3.66(3H.s.CH₃) 3.99(2H.s.CH₂) 7.13-7.48(5H.m.ph)10.87(1H.bs.NH)

IR(CHCl₃)cm⁻¹ : 3432, 1743, 1576.

Anal. Calcd. for C₁₂ H₁₁ N₃ O₄ S C,49.14;H,3.78;N,14.33(%). Found:C,48.81;H,3.79;N,14.31(%).

EXAMPLE 4

A suspension of benzyloxycarbonyl chloride (285 μl; 2.00 mmol) andpotassium thiocyanate (210 mg; 2.17 mmol) in acetonitrile (1.67 ml) wastreated with 3-amino-5-methoxyisoxazole (190 mg; 1.67 mmol) in the samemanner as in Example 1. Since no crystallization was occurred when thereaction mixture was poured into ice-water, the mixture was extractedwith ethyl acetate and the extract was purified by silica gel columnchromatography to give methyl2-(5-benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl) acetate (128 mg;yield 24.9%).

m.p. 121°-123° C. (MeOH)

NMR δ(CDCl₃): 3.70(3H.s.CH₃) 3.85(2H.s.CH₂) 5.33(2H.s.CH₂ Ph)7.35-7.45(5H.m.Ph) 9.96(1H.bs.NH)

IR(CHCl₃)cm⁻¹ : 3404, 1736, 1564.

Anal. Calcd. for C₁₃ H₁₃ N₃ O₄ S: C,50.81;H,4.26;N,13.67(%). Found:C,50.85;H,4.27;N,13.43(%).

In the same manner as described above, the following 1,2,4-thiadiazolecompounds (I) were obtained.

Ethyl 2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate, m.p.102°-104.5° C.;

Ethyl 2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate, m.p.158°-160° C.;

Ethyl 2-(5-benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate, m.p.89°-91° C.;

Ethyl 2-(5-isobutoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate, m.p.64°-66° C.;

Ethyl 2-(5-n-hexyloxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate, m.p.70°-72° C.

EXAMPLE 5

A solution of methyl2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate (48.0 mg;2.08×10⁻¹ mmol), dimethyl sulfoxide (74.0 μl; 1.04 mmol), iodine (5.3mg; 2.1×10⁻² mmol) and concentrated sulfuric acid (0.6 μl) in ethylacetate (480 μl) was stirred under heating with reflux for 3 hours (atthe bath temperature of 100° C.).

The reaction mixture was allowed to cool and then diluted with ethylacetate (1.0 ml), washed with saturated aqueous sodium sulfate solution,saturated aqueous sodium bicarbonate and saturated aqueous sodiumchloride, dried over sodium sulfate, and then concentrated to givemethyl 2-oxo-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate(31.0 mg; yield 60.8%) as a foam.

m.p. 112°-117° C.

NMR δ(CDCl₃): 3.96(3H.s.CH₃), 4.02(3H.s.CH₃), 10.15(1H.bs.NH)

IR(CHCl₃)cm⁻¹ : 3406, 1759, 1546.

EXAMPLE 6

A solution of methyl2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate (52.8 mg;2.15×10⁻¹ mmol), dimethyl sulfoxide (76.5 μl; 1.07 mmol), iodine (5.5mg; 2.2×10⁻² mmol) and concentrated sulfuric acid (0.6 μl) in ethylacetate (528 μl) was treated in the same manner as in Example 5 to givemethyl 2-oxo-2-(5-ethoxylcarbonylamino-1,2,4-thiadiazol-3-yl)acetate(40.8 mg; yield 73.2%) as white crystals.

m.p.: 170°-174° C. (hexane/ethyl acetate)

NMR δ(CDCl₃): 1.40(3H.t.CH₃ CH₂ O) 4.01(3H.s.CH₃ O) 4.41(2H.q.CH₂ O)9.10(1H.bs.NH)

Anal. Calcd. for C₈ H₉ N₃ O₄ S: C,37.06;H,3.50;N,16.21(%). Found:C,37.03;H,3.43;N,16.21(%).

EXAMPLE 7

A solution of methyl2-(5-phenoxycarbonylamino-1,2,4-thadiazol-3-yl)acetate (53.0 mg;1.81×10⁻¹ mmol), dimethyl sulfoxide (64.0 μl; 9.02×10⁻¹ mmol), iodine(4.6 mg; 1.8×10⁻² mmol) and concentrated sulfuric acid (0.5 μl) in ethylacetate (530 μl) was treated in the same manner as in Example 5 to givemethyl 2-oxo-2-(5-phenoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate(24.4 mg; yield 43.9%).

m.p. 74°-79° C.

NMR δ(CDCl₃): 4.00(3H.s.CH₃) 7.25-7.49(5H.m.Ph) 9.45(1H.bs.NH)

EXAMPLE 8

A solution of methyl2-(5-benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate (64.0 mg;2.08×10⁻¹ mmol), dimethyl sulfoxide (74.0 μl; 1.04 mmol), iodine (5.3mg; 2.1×10⁻² mmol) and concentrated sulfuric acid (0.6 μl) in ethylacetate (640 μl) was treated in the same manner as Example 5 to givemethyl 2-oxo-2-(5-benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate(37.5 mg; yield 56.1%).

m.p. 144°-147° C. (hexane/ethyl acetate)

NMR δ(CDCl₃): 4.00(3H.s.CH₃), 5.35(2H.s.CH₂) 7.32-7.49(5H.m.Ph),9.07(1H.bs.NH)

Anal. Calcd. for C₁₃ H₉ N₃ O₅ S:

C,48.60;H,3.45;N,13.08(%). Found: C,48.43;H,3.49;N,13.06(%).

EXAMPLE 9

A solution of methyl2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate (97.8 mg;4.23×10⁻¹ mmol), dimethyl surfoxide (150 μl; 2.11 mmol), iodine (10.7mg; 4.23×10⁻² mmol) and concentrated sulfuric acid (1.2 μl) in ethylacetate (978 μl) was heated to reflux for 3 hours (at the bathtemperature of 100° C.).

After the solution was allowed to cool, 95% aqueous methanol (978 μl)and methoxyamine hydrochloride (42,4 mg; 5.08×10⁻¹ mmol) were added tothe reaction mixture under stirring at room temperature and then thereaction mixture was stirred at the same temperature for 30 minutes.After the reaction was completed, the reaction mixture was directlyconcentrated and the residue obtained was diluted with ethyl acetate(1.0 ml), washed with saturated aqueous sodium thiosulphate, saturatedaqueous sodium bicarbonate, saturated aqueous sodium chloride, driedover sodium sulfate and then concentrated to give methyl2-(5-methoxycarobonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetate(syn-isomer) (119 mg) as white crystals.

m.p. 158°-161° C.(hexane/ethyl acetate)

NMR δ(CDCl₃): 3.94(3H.s.NOCH₃), 3.97(3H.s.COOCH₃) 4.12(3H.s.NHCOOCH₃),8.58(1H.bs.NH)

Anal.Calcd.for C₁₃ H₁₁ N₃ O₅ S: C,48.60;H,3.45; N.13.08(%). Found.:C,48.43;H,3.49;N,13.06(%).

EXAMPLE 10

A mixture of ethyl 2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate (1.29 g; 5 mmol), dimethyl sulfoxide (7.1 ml; 100 mmol), iodine(127 mg; 0.5 mmol) and concentrated sulfuric acid (14 μl; 0.5 mmol) washeated with stirring for 4 hours (at bath temperature of 100° C.). Aftercooling, 95% aqueous methanol (13 ml) and methoxyamine hydrochloride(501 mg; 5×1.2 mmol) were added thereto and the reaction mixture wasstirred for 3 hours at room temperature. Further, 5N sodium hydroxideaqueous solution (1.3 ml; 5×1.3 mmol) was added thereto and the mixturewas stirred at room temperature for 1 hour. The solvent was thoroughlyevaporated under reduced pressure and ethyl acetate (20 ml) was added tothe residue. The mixture was washed with aqueous saturated sodiumthiosulfate (2.5 ml), saturated aqueous sodium bicarbonate (2.5 ml) andsaturated aqueous sodium chloride (2.5 ml×2), dried over sodium sulfatewas concentrated to remove ethyl acetate and then dried under vacuum togive ethyl2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetate(syn-isomer) (1.32 g; 87.6%).

m.p. 108°-110° C. (hexane/ethyl acetate)

IR(KBr)cm⁻¹ : 2990, 1718, 1548, 1235, 1033.

¹ HNMR δ(CDCl₃): 1.36(6H.t.J=7 Hz), 3.98(3H.s), 4.28(2H.q.J=7 Hz),4.36(2H.q.J=7 Hz), 7.56(1H.bs)

EXAMPLE 11

Ethyl 2-(5-benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate (1.6 g;5 mmol) was treated in the same manner as in Example 10 to give ethyl2-(benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetate(syn-isomer) (1.6 g; 91.7%) as a syrup.

¹ HNMR δ(CDCl₃): 1.34(3H.t.J=7 Hz), 3.92(3H.s) 4.36(2H.q.J=7 Hz),5.21(2H.s), 7.26(5H.s)

EXAMPLE 12

Ethyl2-(5-benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetate(syn-isomer) (1.44 g; 4.11 mmol) was dissolved in ethanol (14 ml) and 2NNaOH (4.11 ml; 8.22 mmol) was added thereto at room temperature. Thereaction mixture was stirred at the room temperature for 2 hours.Ethanol was evaporated under reduced pressure and the residue wasdissolved in water (15 ml). The mixture was washed twice with ethylacetate (10 ml) and acidified with 6N hydrochloric acid (1.6 ml) topH 1. After cooling, the crystals formed were filtered off, washed withwater and then dried under reduced pressure to give2-(5-benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoaceticacid (syn-isomer) (1.02 g; 73.8%).

m.p. 138°-142° C.

IR (KBr₆)cm⁻¹ : 3170, 1710, 1545, 1228, 1040.

¹ HNMR δ(DMSO-d₆): 3.93(3H.s), 5.25(2H.s), 5.85(2H.bs) 7.31(5H.s)

EXAMPLE 13

To ethyl2-(5-ethoxycarbonylamino-1,2,4-thiadiazole-3-yl)-2-methoxyiminoacetate(syn-isomer) (302 mg; 1.0 mmol) was added 1N sodium hydroxide (6.0 ml;6.0 mmol) and the reaction mixture was refluxed for 5 hours (at the bathtemperature of 110° C.). After cooling, the mixture was acidified with6N hydrochloric acid (1.0 ml) to pH 1. The mixture was extracted withethyl acetate (0.3 ml×5) and the extract was dried over sodium sulfateand then concentrated to give2-(5-amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid (syn-isomer)(102 mg; 50,4%).

m.p. 179°-181° C.

EXAMPLE 14

A solution of ethyl2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetate(19.6 mg; 7.15×10⁻² mmol) in aqueous 1N NaOH solution (286 μl; 286×10⁻¹mmol) was stirred at 100° C. for 4 hours. After cooling, the mixture wasacidified with 6N hydrochloric acid to pH 1. The mixture was extractedwith ethyl acetate (0.3 ml×5) and the extract was dried over sodiumsulfate and then concentrated to give2-(5-amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid (10.8 mg;yield 74.7%) as white crystals.

m.p. 179°-181° C.

NMR δ(DMSO-d₆): 3.90(3H.s.CH₃), 8.20(2H.bs. NH₂)

EXAMPLE 15

3-amino-5-methoxyisoxazole (1.2 g) was dissolved in tetrahydrofuran (10ml) and benzoylisothiocyanate (2.2 g) was added dropwise thereto at2°-3° C. After the mixture was stirred for 1 hour, the reaction mixturewas poured into ice-water and then the formed crystals were filteredoff. After washing with water and isopropylether, the crystals wasdissolved in ethanol (50 ml) with warming. The solution was concentratedunder reduced pressure to give methyl2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)acetate (1.6 g, 57.7%).

m.p. 143°-144.5° C.

NMR δ(CDCl₃): 3.68(3H,s,--COOOCH₃), 3.81(2H,s,CH₂), 7.05-8.0(5H,m,--C₆H₅)

IR(KBr)cm⁻¹ : 1720, 1660, 1540.

EXAMPLE 16

3-amino-5-ethoxyisoxazole (1.3 g), tetrahydrofuran (10 ml) andbenzoylisothiocyanate (2.1 g) were treated in the same manner as inExample 15, to give ethyl 2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)acetate 2.0 g (68.7%).

m.p. 119.0°-120.5° C.

NMR δ(CDCl₃): 1.2(3H,t,CH₃ --) 3.7(2H,s,--CH₂ --), 4.1(2H,q,--OCH₂),7.2-8.1(5H,m,--C₆ H₅), 11.2(1H,brs,NH)

IR(KBr)1270cm⁻¹ : 1720, 1670, 1530.

EXAMPLE 17

A solution of 4-nitrobenzoyl chloride (3.8 g) and potassium thiocyanate(2.5 g) in toluene (20 ml) was heated with stirring at 80°-90° C. for 5hours. After the insoluble matter was filtered, the filtrate wasconcentrated to give p-nitrobenzoylisothiocyanate 3.3 g. The product wasdissolved in tetrahydrofuran (20 ml) and 3-amino-5-ethoxyisoxazole (2 g)was added thereto at 2°-4° C. After the reaction mixture was stirred for2 hours, the mixture was poured into ice-water and the formedprecipitates were filtered. After the precipitates were washed withwater and isopropylether, ethanol (100 ml) was added thereto and themixture was stirred at 40° C. for 30 minutes. After the formedprecipitates were filtered, recrystallized with ethyl acetate/isopropylether to give ethyl2-(5-(4-nitrobenzoylamino-1,2,4-thiadiazol-3-yl)acetate.

m.p. 178.0°-180.5° C.

NMR δ(DMSO-d₆): 3.9(2H,s,--CH₂ --), 4.1(2H,q,--OCH₂ --), 8.27(4H,s,C₆ H₄--), 14(1H,brs,--NH), 1.17(3H,t,--CH₃)

IR(KBr)cm⁻¹ : 1710, 1670, 1520-40.

EXAMPLE 18

3-amino-5-ethoxyisoxazole (1.3 g) was dissolved in tetrahydrofuran (10ml) and 3,4-difluoroisocyanate (1.7 g) was added thereto. The mixturewas reacted at 2°-3° C. for 1.5 hours and then at room temperature.After the solvent was evaporated, water was added thereto and thecrystals were filtered. The obtained crystals were dissolved withethanol and the mixture was warmed at 40°-50° C. for 30 minutes and thenconcentrated to give ethyl2-(5-(3,4-difluorophenylamino)-1,2,4-thiadiazol-3-yl) acetate (0.25 g).

m.p. 84°-90° C.

NMR δ(CDCl₃): 1.27(3H,t,CH₃ --), 3.77(2H,s,--CH₂ --), 4.17(2H,q,--OCH₂CH₃), 6.83-7.57(3H,m,C₆ H₃ F₂ --), 8.83(1H,brs,NH)

IR(KBr)cm⁻¹ : 1700, 1620, 1560, 1510.

EXAMPLE 19

A solution of methyl 2-(5-benzoylamino-1,2,4-thiadiazol-3-yl) acetate (5g), dimethyl sulfoxide (24 ml) and iodine (0.63 g) in concentratedsulfuric acid (0.064 ml) was heated at 100° C. for 4 hours and cooled.Then ethyl acetate (200 ml) was added thereto. The mixture was washedwith saturated aqueous sodium thiosulfate, saturated aqueous sodiumbicarbonate and saturated aqueous sodium chloride, dried over sodiumsulfate and concentrated to give methyl2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-2-oxo-acetate 1.4 g.

m.p. 164°-166.5° C.

NMR δ(CDCl₃): 3.95(3H,s,COOCH₃), 7.1-8.1(5H,m,C₆ H₅ --),14.1(1H,brs,--CONH)

IR(KBr)cm⁻¹ : 1720-1700, 1520, 1280.

EXAMPLE 20

Ethyl 2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)acetate (2 g), dimethylsulfoxide (12 ml), iodine (0.19 g) and concentrated sulfuric acid (0.019ml) were treated in the same manner as in Example 19 to give ethyl2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-2-oxo-acetate 0.7 g.

m.p. 178°-179.5° C.

NMR δ(CDCl₃): 1.0(3H,t,--CH₃), 4.4(2H,q,COOCH₂ CH₃), 7.3-8.2(5H,m,C₆H₅), 14.2(1H,brs,--CONH)

IRcm⁻¹ : 1720-1700, 1660, 1530, 1280.

EXAMPLE 21

A solution of methyl2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetate(13.7 g, 0.05 mol) and sodium hydroxide (4.49 g, 0.11 mol) in water (112ml) was reacted with stirring for 1 hour. After the reaction wascompleted, the reaction mixture was acidified to pH 1 with 35%hydrochloric acid, extracted with ethyl acetate and dried over sodiumsulfate and concentrated to give2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoaceticacid 9.8 g (yield 75.7%).

m.p. 178°-180° C. (decomposition)

EXAMPLE 22

A solution of methyl2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetate (32 g,0.1 mol), sodium hydroxide (16 g, 0.4 mol) in water (400 ml) was reactedwith stirring at room temperature for 3 hours. After the reaction wascompleted, the reaction mixture was acidified to pH 1 with 35%hydrochloric acid and the formed precipitates were filtered off andwashed with water and isopropyl ether and then dried under reducedpressure to give2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid 29.7g (yield 97.4%).

m.p. 198°-200° C. (decomposition)

EXAMPLE 23

(a)2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoaceticacid (5 g, 0.019 mol), 25% aqueous ammonia (7.1 g) and water (93 g) werecharged in a pressure container and heated at 100° C. for 40 hours.After completion of the reaction, the reaction mixture was distilledunder reduced pressure to remove ammonia and then acidified with 2Nhydrochloric acid to pH 1 and extracted with ethyl acetate. The extractwas dried over sodium sulfate and concentrated to give white crystals(3.5 g). White crystals obtained as above were recrystallized frommethanol/H₂ O and the obtained crystals were dried under reducedpressure to give 2-(5-amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoaceticacid (1.75 g, yield 45%).

Purity: by HPLC 85%

(b) 2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-2-methoxy-iminoacetic acid(20 g, 0.065 mol) and 14% aqueous ammonia were charged in 500 mlpressure container and heated at 100° C. 40 hours. After completion ofthe reaction, the reaction mixture was distilled to remove ammonia andconcentrated to about half volume. The concentrate was acidified with 2NHCl to pH 2-3 and extracted with ethyl acetate. The aqueous layer wasacidified with concentrated HCl to pH 1, and sodium chloride was addedthereto. Then the solution was extracted with ethyl acetate and theextract was dried over sodium sulfate and concentrated to give whitecrystals (10 g).

White crystals as above described was washed with ethyl acetate anddried under reduced pressure to give2-(5-amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid (yield 9.6g, 78.6%).

Purity: by HPLC 97.5%

m.p. 174°-175° C. (decomposition)

(c) A solution of2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid (7.5g, 0.0245 mol) and diethanolamine (12.9 g, 0.123 mol) in water (130 g)was heated at 100° C. for 24 hours. After completion of the reaction,the reaction mixture was applied to column of strong acid cationexchange resin (150 ml) and the resin was washed with ion exchange water(1000 ml). The eluent was combined with washings and the mixture wasconcentrated to about 300 ml. The concentrate was extracted withisopropyl ether and aqueous layer was concentrated. The formed crystalswere filtered off and dried under reduced pressure to give2-(5-amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid (4.2 g,yield 84.8%).

Purity: by HPLC 96.2%

(d) A solution of2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid (153mg) in 5% aqueous butylamine was reacted at 100° C. for 40 hours to give2-(5-amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid.

(e) A solution of2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid (200mg) in 8% aqueous methylamine (2.5 ml) was reacted at 100° C. for 40hours to give 2-(5-amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoaceticacid.

EXAMPLE 24

(a) To a suspension of potassium thiocyanate (47.5 g, 0.49 mol) inacetonitrile 300 ml was added dropwise methyl chloroformate (43.0 g,0.46 mol) and the mixture was stirred at 70° C. for 30 minutes. Then3-aminoisoxazole (29.4 g, 0.35 mol) was added dropwise to the mixtureunder ice-cooling and stirring. The mixture was stirred for 30 minutesat the same temperature and then for 15 minutes at room temperature. Thereaction mixture was poured into ice-water (800 ml) and the precipitatesformed were filtered off, washed with water and then dried under reducedpressure to give 1-(isoxazol-3-yl)-3-methoxycarbonylthiourea (36 g).

Yield 51.2%. m.p. 165°-167° C. (ethyl acetate/hexane).

NMR δ(CDCl₃): 3.85(3H,s,COOCH₃), 7.36(1H,w,J=2 Hz), 8.28(1H,w,J=2 Hz),8.50(1H,bs,--NHCS--), 10.50(1H,bs,NH).

IR(KBr)cm⁻¹ : 1730, 1596, 1549, 1342, 1245, 1200.

(b) 1-(isoxazol-3-yl)-3-methoxycarbonylthiourea (30 g, 0.15 mol)obtained in Example 24(a) as described above was heated in methanol (200ml) at 30°-35° C. for 1 hour. After cooling, the crystals formed werefiltered off. Isopropyl ether (50 ml) was added to the mother liquor andthe precipitates formed were filtered off, combined with the formercrystals and concentrated under reduced pressure to give2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetaldehyde (28.5 g).Yield 98%.

m.p. 164°-166° C. (MeOH).

NMR δ(CDCl₃): 3.90(2H,w,J=2 Hz), 3.92(3H,s,COOCH₃), 9.87(1H,t,CHO),10.50(1H,bs,NH).

IR(KBr)cm⁻¹ : 2955, 1720, 1565, 1295, 1245, 1110.

(c) 2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetaldehyde (3.72g, 18.5 mmol) obtained in Example 24(b) as described above was dissolvedin a mixture of t-butanol (50 ml) and water (5 ml) and then peraceticacid (20 ml, 86.8 mmol) was added dropwise thereto under ice-cooling.The temperature was elevated to 20° C. and then the reaction mixture wasstirred overnight at the same temperature while the reaction wascontinued. After completion of the reaction, excess peracetic acid wasdecomposed with aqueous 30% sodium bisulfite solution and then thecrystals formed were filtered off. The filtrate was concentrated up to1/3 the original volume of and the crystals formed was filtered offafter cooling. The crystals were combined with the former crystals andthen dried under reduced pressure to give2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetic acid (3.2 g).Yield 80.0%.

m.p. 188°-190° C. (MeOH)

NMR δ(DMSO-d₆): 3.90(2H,w,J=2 Hz), 3.92(3H,s), 10.50(1H,bs,--NH--).

IR(KBr)cm⁻¹ : 2959, 1720, 1555, 1355.

EXAMPLE 25

(a) A suspension of ethyl chloroformate (6.51 g, 0.06 mol) and potassiumthiocyanate (6.31 g, 0.065 mol) in acetonitrile (60 ml) was treated with3-aminoisoxazole (4.2 g, 0.05 mol) in the same manner as Example 24(a)and the precipitates formed were filtered off, washed with water andthen dried under reduced pressure (yield 5.20 g).

This product was identified to be a mixture of1-(isoxazol-3-yl)-3-ethoxycarbonylthiourea and2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)-acetaldehyde by NMRanalysis.

NMR δ(CDCl₃): 1.24(t,J=7 Hz), 3.92(w,J=2 Hz), 4.23(q,J=7 Hz), 7.38(w,J=2Hz), 8.28(w,J=2 Hz), 9.05(bs,--NHCS--), 9.87(t,CHO), 10.50(bs,NH).

(b) The crystals obtained (5.16 g) in Example 25(a) as described abovewere heated in methanol (100 ml) at 40°-45° C. for 2 hours and treatedthen in the same manner. The crystals were filtered off and dried underreduced pressure to give2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetaldehyde (4.90 g).Yield 45.6% (from 3-aminoisoxazole).

m.p. 152°-154° C.(MeOH)

NMR δ(CDCl₃): 1.23(3H,t,J=7 Hz), 3.90(2H,w,J=2 Hz), 4.22 (2H,q,J=7 Hz)9.87(1H,t,CHO), 10.50(1H,bs,NH)

IR(KBr)cm⁻¹ : 2960, 1719, 1580, 1275, 1245.

(c) 2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl) acetaldehyde (4.02g, 18.7 mmol) obtained in Example 25(b) as described above was dissolvedin ethyl acetate (70 ml) and treated in the same manner as in Example24(c) the crystals were filtered off and dried under reduced pressure togive 2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetic acid (3.4 g).(yield 78%).

m.p. 170°-172° C.(MeOH)

NMR (DMSO-d₆): 1.24 (3H,t,J=7 Hz), 3.91(2H,W,J=2 Hz), 4.24(2H,g,J=7 Hz),10.52(1H,bs,NH).

IR(KBr)cm⁻¹ : 2962, 1719, 1557, 1358.

EXAMPLE 26

(a) A suspension of acetyl chloride (9.42 g, 0.12 mol) and potassiumthiocyanate (12.62 g, 0.13 mol) in acetonitrile (100 ml) was heated at70° C. for 3 hours and then 3-aminoisoxazole (8.4 g, 0.1 mol) was addeddropwise thereto under ice-cooling and stirring. The mixture was stirredfor 1 hour at the same temperature and then for 1 hour at roomtemperature. Then the reaction mixture was poured into ice-water (250ml) and the mixture was stirred for 1 hour. The precipitates formed werefiltered off, washed with water and then dried under reduced pressure(yield 7.5 g).

This product was identified to be a mixture of1-(isoxazol-3-yl)acetylthiourea and2-(5-acetylamino-1,2,4-thiadiazol-3-yl)acetaldehyde by NMR analysis.

NMR δ(CDCl₃): 2.25(s,COCH₃), 3.90(w,J=2 Hz), 7.33(w,J=2 Hz), 8.88(w,J=2Hz), 9.87(t,CHO), 10.81(bs,--NHCS--), 12.60(bs,--NH--)

(b) The crystals (7.45 g) obtained in Example 26(a) as described abovewere heated in methanol (150 ml) at 40°-45° C. for 1 hour and treated inthe same manner as in Example 25. The crystals were filtered off anddried under reduced pressure to give2-(5-acetylamino-1,2,4-thiadiazol-3-yl)acetaldehyde (7.05 g). Yield 32%(from 3-aminoisoxazole).

m.p. 145°-147° C. (MeOH)

NMR δ(CDCl₃): 2.23(3H,s), 3.92(2H,w,J=2 Hz), 9.87(1H,t,CHO),10.80(1H,b,--NH--).

IR(KBr)cm⁻¹ : 2955, 1695, 1660, 1575, 1225.

(c) 2-(5-acetylamino-1,2,4-thiadiazol-3-yl)acetaldehyde (6.2 g, 33.5mmol) obtained in Example 26(b) as described above was dissolved inethyl acetate (100 ml), and treated in the same manner as Example 25(c).The crystals were filtered off and dried under reduced pressure to give2-(5-acetylamino-1,2,4-thiadiazol-3-yl)acetic acid (5.1 g, yield 75%).

m.p. 161°-163° C.(MeOH)

NMR δ(DMSO-d₆): 2.24(3H,s), 3.93(2H,W,J=2 Hz), 16.80(1H,bs,--NH--)

IR(KBr)cm⁻¹ : 2958, 1698, 1665, 1550.

EXAMPLE 27

(a),(b) A suspension of phenylchloroformate (2,9 g, 18.5 mmol) andpotassium thiocyanate (1.95 g, 20 mmol) in acetonitrile (20 ml) wastreated with 3-aminoisoxazole (1.4 g, 16.7 mmol) and treated in the samemanner as in Example 24(a),(b). The crystals were filtered off and driedunder reduced pressure to give2-(5-phenoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetaldehyde (1.1 g,yield 25%).

m.p 159°-162° C.(MeOH)

NMR δ(CDCl₃): 3.92(2H,W J=2 Hz), 7.15-7.53(5H,m,ph), 9.87(1H,t,CHO),10.85(1H,bs,--NH--)

IR(KBr)cm⁻¹ : 3090, 1729, 1590.

(c) 2-(5-phenoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetaldehyde (1.0 g,3.8 mmol) was dissolved in dichloroethane (30 ml) and treated in thesame manner as in Example 24(c). The crystals were filtered off anddried under reduced pressure to give2-(5-phenoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetic acid (798 mg,yield 75%).

m.p. 174°-176° C. (MeOH)

NMR δ(DMSO-d₆): 3.92(2H,W,J=2 Hz), 7.16-7.54(5H,m,ph),10.86(1H,bs,--NH--).

IR(KBr)cm⁻¹ : 3095, 1730, 1595.

EXAMPLE 28

(a) A suspension of benzoyl chloride (9 g, 64.3 mmol) and potassiumthiocyanate (11.3 g, 0.116 mmol) in acetonitrile (40 ml) was heated at70° C. for 6 hours and then cooled. Potassium chloride was filtered,acetonitrile was removed from the filtrate and the residue was driedunder reduced pressure to give benzoylisothiocyanate (6.3 g, 95°-96°C./5 mmHg).

The obtained benzoylisothiocyanate (6.3 g, 38.7 mmol) was dissolved inacetonitrile (50 ml). 3-aminoisoxazole (2.8 g, 33.3 mmol) was addeddropwise thereto. The mixture was stirred at the same temperature for 1hour and then treated in the same manner as in Example 26(a). Thecrystals were filtered off and dried under reduced pressure to give amixture (6.5 g) of 1-(isoxazol-3-yl)-benzoylthiourea and2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)acetaldehyde.

(b) The crystals (6.5 g) obtained in Example 28(a) as described abovewere treated in the same manner as in Example 26(b) and the crystalswere filtered off and dried under reduced pressure to give2-(5-benzoylamino-1,2,4-thiadiazole-3-yl)acetaldehyde (6.4 g). Yield77.5% (from 3-aminoisoxazol).

m.p. 153°-155° C.(MeOH)

NMR δ(CDCl₃): 3.92(2H,W,J=2 Hz), 7.63-8.26(5H,m,ph), 9.86(1H,t,CHO),10.84(1H,bs,--NH--).

IR(KBr)cm⁻¹ : 3010, 1698, 1662, 1570.

(c) 2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)acetaldehyde (6 g, 24.2mmol) obtained in Example 28(b) as described above was dissolved indichloroethane (180 ml) and treated then in the same manner as inExample 24(c). The crystals were filtered off and dried to give2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)acetic acid (4.98 g, yield 78%).

m.p. 173°-175° C. (MeOH)

NMR δ(DMSO-d₆): 3.92(2H,W,2 Hz), 7.63-8.26(5H,m,ph), 10.85(1H,bs,--NH--).

IR(KBr)cm⁻¹ : 3014, 1670, 1560.

EXAMPLE 29

(a),(b) A suspension of p-nitrophenyl chloroformate (4.07 g, 20.2 mmol)and potassium thiocyanate (2.12 g, 21.7 mmol) in acetonitrile (100 ml)was treated with 3-aminoisoxazole (1.3 g, 15.5 mmol) in the same manneras in Example 24-(a),(b). The crystals were filtered off and dried underreduced pressure to give2-(5-p-nitrophenoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetaldehyde(0.91 g). Yield 20%.

m.p. 172°-175° C.(MeOH)

NMR δ(CDCl₃): 3.92 (2H,W,J=2 Hz), 7.68-8.83(4H,m,ph), 9.87 (1H,t,CHO),10.86 (1H,bs,--NH--).

IR(KBr)cm⁻¹ : 3092, 1730, 1595.

(c) 2-(5-p-nitrophenoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetaldehyde(0.8 g, 2.7 mmol) was dissolved in dichloroethane (20 ml) and treated inthe same manner as in Example 24(c). The crystals were filtered off anddried under reduced pressure to give2-(5-p-nitrophenoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetic acid (0.71g). Yield 84%.

EXAMPLE 30

3-aminoisoxazole (155 g) was dissolved in tetrahydrofuran (776 ml) andbenzoylisothiocyanate (354 g) was added dropwise thereto. The reactionmixture was poured into ice-water after stirring for 1 hour and1-(isoxazol-3-yl)benzoylthiourea was filtered off. This crystals weredissolved in ethanol (2200 ml) and the solution was heated at 50° C. for30 minutes and then cooled to give2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-1-ethoxy-1-ethanol (454 g,83.8%).

m.p. 127°-128° C.(decomposition)

NMR δ(DMSO-d₆): 1.05(3H,t,--CH₂ --CH₃), 2.70(2H,W,--CH₂ --),3.50(2H,m,O--CH₂ --CH₃), 5.10(1H,q,--CH═), 6.08(1H,W,--OH),7.52-8.25(5H,m,ph), 13.4 (1H,bs,--NH--)

IR(KBr)cm⁻¹ : 3161, 1664, 1548, 1323, 1128.

EXAMPLE 31

1-(isoxazol-3-yl)benzoylthiourea obtained from 3-aminoisoxazole (7.8 g)in the same manner as Example 30 was dissolved in acetone and thesolution was allowed to react overnight at ordinary temperature and thencooled to give 2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)acetaldehyde (4.7g, yield 38%).

m.p. 149° C.-152° C. (decomposition)

NMR δ(DMSO-d₆): 4.0(2H,d,--CH₂ --),7.4-8.2(5H,m,ph), 9.7(1H,t,CHO),13.3(1H,brs,--NH--),

IR(KBr)cm⁻¹ : 1668, 1540, 1290.

EXAMPLE 32

2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-1-ethoxy-1-ethanol (60 g) wasdissolved in acetic acid (600 g) and 38% peracetic acid (48 g) was addeddropwise thereto at 40° C. After the mixture was reacted for 6.5 hours,aqueous sodium bisulfite was added thereto and acetic acid was removedby distillation of the mixture. The concentrate was poured into waterand the precipitated 2-(5-benzoyl-1,2,4-thiadiazol-3-yl)acetic acid wasfiltered off. yield 51.3 g (95.3%)

m.p.172°-174° C.

NMR δ(DMSO-d₆): 3.87(2H,s,--CH₂ --), 7.52-8.25(5H,m,ph)

IR(KBr)cm⁻¹ : 3172, 1693, 1668, 1545, 1286.

EXAMPLE 33

4-fluorobenzoylchloride (79.2 g) and potassium thiocyanate (58.6 g) wasrefluxed in toluene (200 ml) for 10 hours. The reaction mixture wasdistilled to give 4-fluorobezoylisothiocyanate (69.7 g). The productobtained as above (24 g) was dissolved in tetrahydrofuran (100 ml),3-aminoisoxazole 10 g was added dropwise at 0°-3° C. and the mixture wasstirred. The reaction mixture was poured into ice-water and theprecipitate formed was filtered off and washed with water andisopropylether. The obtained thiourea derivative was dissolved inethanol and the solution was stirred at 40°-50° C.5-(4-fluorobenzoylamino-1,2,4-thiadiazol-3-yl)acetaldehyde hemiacetalwas formed and filtered off. Yield 22.5 g(60.2%).

m.p. 129°-131° C.

NMR δ(DMSO-d₆) 1.1(3H,t,--CH₃), 3.0(2H,W,--CH₂), 3.2-3.9(m,2H,--O--CH₂), 5.1 (1H,q,CH), 6.1(1H,W,OH), 7.1-8.3(m,4H,ph), 13.5(1H,bs,NH)

IR(KBr)cm⁻¹ : 1666, 1597, 1551, 1514, 1311.

EXAMPLE 34

5-(4-fluorobenzoylamino)-1,2,4-thiadiazol-3-yl)acetaldehyde hemiacetal(20 g) was dissolved in acetic acid (200 ml) and 39% peracetic acid(17.7 g) was added thereto. After the mixture was allowed to reactovernight at 40°-45° C., an aqueous sodium hydrogensulfite aqueoussolution was added thereto. The reaction mixture was concentrated underreduced pressure and then the concentrate was treated in the same manneras in Example 32 to give5-(4-fluorobenzoylamino)-1,2,4-thiadiazol-3-yl)acetic acid (9.4 g, yield76%).

m.p. 189.5°-191.0° C.

NMR δ(DMSO-d₆): 3.9(2H,s,--CH₂ --), 7.2-8.4(4H,m,ph)

IR(KBr)cm⁻¹ : 1693.4, 1672.2, 1598.9, 1544.9, 1242.1.

EXAMPLE 35

1-(isoxazol-3-yl)-benzoylthiourea obtained from 3-aminoisoxazole (3.2 g)in the same manner as in Example 30, was dissolved in methanol and themixture was heated at 40° C. for 1.5 hours. The mixture was cooled togive 2-(5-benzoylamino-1,2,4-thiadiazol-3-yl)-1-methoxy-1-ethanol (8.6g, 80%).

m.p. 103°-105° C.(decomposition)

NMR δ(DMSO-d₆): 2.52 (2H,W,--CH₂), 3.05(3H,S.--OCH₃), 4.83(1H,q,--CH═),5.98(1H,W,--OH), 7.25-7.95(5H,m,ph), 13.3 (1H,bs,NH)

IR(KBr)cm⁻¹ : 3350, 1647, 1579, 1552, 1332, 1114.

EXAMPLE 36

(A) Into a solution of methyl2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate (230 mg,9.96×10⁻¹ mmol) and concentrated hydrochloric acid (12.4 ml, 1.49×10⁻¹mmol) in tetrahydrofuran (2.30 ml) was bubbled, over 10 minutes, methylnitrite (MeONO) gas which was prepared by gradually dropping 12Nhydrochloric acid aqueous solution (500 μl, 6.00 mmol) to a suspensionof sodium nitrite (137 mg, 1.99 mmol) in 50% aqueous methanol (242 μl).The reaction mixture was directly concentrated after stirring for 1 hourat the same temperature. Ether (5 ml) was added to the obtained residue.White crystals formed were filtered off, washed with ether (1 ml×3) andthen dried under reduced pressure to give methyl(Z)-2-hydroxyimino-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate(227 mg, yield 87.6%).

m.p. 187°-190° C. (CHCl₃)

NMR (CDCl₃): 3.96 (3H,s,COOCH₃), 4.02 (3H,s,NHCOOCH₃), 9.45(1H,bs,NH orNOH), 9.92(1H,bs,NOH or NH)

Anal. Calcd. for C₇ H₈ N₄ O₅ S:

C,32.31;H,3.10;N,21.53 (%). Found: C,32.17;H,2.99;N,21.42(%).

(B) To a suspension of methyl(Z)-2-hydroxyimino-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate(21.1 mg, 8.11×10⁻² mmol), barium oxide (62.2 mg, 4.05×10⁻¹ mmol) andbarium hydroxide 8 hydrate (12.8 mg, 4.05×10⁻² mmol) indimethylformamide (422 μl) and chloroform (150 μl), was added dimethylsulfate (8.4 μl, 8.9×10⁻² mmol) under stirring at room temperature. Thereaction mixture was diluted with ethyl acetate (0.5 ml) after stirringfor 30 min at the same temperature. Pieces of dry ice were addedthereto. The resulting insoluble matter was filtered through a layer ofCelite and the residue was washed with ethyl acetate (0.5 ml×3). Thefiltrate was combined with the washings and the mixture was washed withsaturated sodium chloride, dried over sodium sulfate and thenconcentrated to give methyl(Z)-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxy-iminoacetate(13.2 mg, yield 59.3%) as white crystals.

m.p. 158°-161° C. (However, either barium oxide or barium hydroxide onlywas used in the reaction (E)-isomer was formed.)

(C) A solution of methyl(Z)-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetate(19.6 mg, 7.15×10⁻² mmol) in aqueous 1N sodium hydroxide (286 μl,2.86×10⁻¹ mmol) was stirred for 4 hours at 100° C., and then 1Nhydrochloric acid (290 μl, 2.90×10⁻¹ mmol) was added dropwise theretounder ice-cooling and stirring (pH=1). The mixture was extracted withethyl acetate (0.3 ml×5), and the extract was dried over sodium sulfateand then concentrated to give(Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid (10.8mg, yield 74.7%) as white crystals.

NMR δ(DMSO-d₆): 3.90(3H,s,CH₃), 8.20(2H,bs,NH₂)

EXAMPLE 37

(A) A solution of methyl chloroformate (53.3 μl, 6.90×10⁻¹ mmol) andpotassium thiocyanate (72.6 mg, 7.47×10⁻¹ mmol) in anhydroustetrahydrofuran (575 μl) was stirred for 1 hour at 70° C., and then3-amino-5-methoxyisoxazole (65.6 mg, 57.5×10⁻¹ mmol) was added to thereaction mixture under ice-cooling and stirring. The mixture was stirredfor 30 minutes at the same temperature and further for 12 hours at roomtemperature. After the reaction was completed, residual potassiumthiocyanate was decomposed by adding water (72.6 μl) to the reactionmixture at the same temperature and then residual potassium thiocyanatewas disintegrate by stirring for 3 hours to give methyl(5-amino-1,2,4-thiadiazol-3-yl)acetate. Then concentrated hydrochloricacid (10.0 μl) was added to the product and methyl nitrite (1.73 mmol;prepared from 120 mg sodium nitrite, 140 μl 50% aqueous methanol, 500 μl12N H₂ SO₄) was bubbled thereinto. The reaction mixture was directlyconcentrated after stirring at the room temperature for 1 hour, theresidue was dissolved in ethyl acetate (500 μl). The solution was washedwith saturated aqueous sodium chloride, dried over sodium sulfate andthen concentrated to give methyl(Z)-2-(5-methoxy-carbonylamino-1,2,4-thiadiazol-3-yl)2-hydroxyiminoacetate(124 mg, yield 82.9%) as pale yellow crude crystals.

(B) A suspension of methyl(Z)-2-hydroxyimino-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate(21.6 mg, 8.30×10⁻² mmol), ethyl bromoacetate (10.1 μl, 9.13×10⁻² mmol),barium oxide (63.6 mg, 4.15×10⁻² mmol) and barium hydroxide 8 hydrate(21.0 mg, 6.64×10⁻² mmol) in dimethylformamide (400 μl) and chloroform(200 μl) was stirred for 1.5 hours under ice-cooling. After the reactionwas completed, the reaction mixture was diluted with ethyl acetate.Pieces of dry ice were added thereto. The resulting insoluble matter wasfiltered through a layer of Celite. The residue was washed with ethylacetate (0.5 ml×3), the filtrate was combined with the washings and themixture was washed with saturated aqueous sodium chloride, dried oversodium sulfate and then concentrated to give methyl(Z)-2-ethoxy-carobonylmethloxyimino-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetateas yellow crude crystals (24.2 mg, yield 84.2%).

EXAMPLE 38

Ethyl(Z)-2-(5-benzyloxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetate1.44 g (4.11 mmol) was dissolved in ethanol (14 ml) and 2N sodiumhydroxide solution (4.11 ml, 8.22 mmol) was added thereto at roomtemperature. The mixture was stirred at room temperature for 2 hours.Ethanol was evaporated under reduced pressure. The residue was dissolvedin water (15 ml), washed with ethyl acetate (10 ml) twice, acidifiedwith 6N hydrochloric acid (1.6 ml) to pH 1. The reaction mixture wascooled and the crystals formed were filtered off, washed with water andthen dried under reduced pressure to give(Z)-2-(5-benzyloxycarbonylamino1,2,4-thiadiazol-3-yl)-2-methoxyiminoaceticacid (1.02 g, 73.8%).

m.p. 138°-142° C.

IR(KBr)cm⁻¹ : 3170, 1710, 1545, 1228, 1040.

¹ HNMR δ(DMSO-d₆): 3.93(3H,s), 5.25(2H,s), 5.85(2H,bs), 7.31(5H,s)

EXAMPLE 39

To ethyl(Z)-2-(5-ethoxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetate(302 mg, 1.0 mmol) was added 1N sodium hydroxide (6.0 ml, 6.0 mmol) andthe mixture was refluxed for 5 hours at the bath temperature of 110° C.The reaction mixture was cooled, acidified with 6N hydrochloric acid(1.0 ml) to pH 1 and extracted with ethyl acetate (4 ml). The extractwas dried over sodium sulfate and then concentrated to give(Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetic acid (102 mg,50.4%)

The physicochemical data of the product corresponded to those of theproduct obtained in Example 36(c).

EXAMPLE 40

To a suspension of methyl(Z)-2-hydroxyimino-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate(10.5 mg, 4.03×10⁻² mmol) and silver oxide (28.1 mg, 1.21×10⁻¹ mmol) inanhydrous dimethylformamide (100 ml) was added, methyl iodide (7.5 μl,1.21×10⁻¹ mmol) under stirring at room temperature. The reaction mixturewas stirred for 1 hour and then filtered through a layer of Celite. Theresidue was washed with ethyl acetate (1.0 ml×3). The filtrate wascombined with washings and the mixture was concentrated to give crudesyrup (17.3 mg, 100%). This was purified by column chromatography (0.3 gKiesergel, hexane/ethyl acetate: 1/1) to give methyl(Z)-2-(5-methoxy-carbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetateas white crystals (8.8 mg, 79.6%).

EXAMPLE 41

To a suspension of methyl(Z)-2-hydroxyimino-2-(5-methoxy-carbonylamino-1,2,4-thiadiazol-3-yl)acetate(7.2 mg, 2.8×10⁻² mmol), barium oxide(2.33 mg, 1.52×10⁻¹ mmol) andbarium hydroxide 8 hydrate (7.0 mg, 2.2×10⁻² mmol) in anhydrousdimethylformamide (150 μl) and anhydrous chloroform (60 μl) was added,methyl iodide (2.1 μl, 3.3×10⁻² mmol) was added under stirring at roomtemperature. The reaction mixture was stirred at the same temperaturefor 30 minutes and then diluted with ethyl acetate (0.5 ml). Pieces ofdry ice broken was introduced thereto. The insoluble matter was filteredthrough a layer of Celite and the residue washed with ethyl acetate (0.5ml×3). The filtrate was combined with the washings and the mixture waswashed with saturated sodium chloride, dried over sodium sulfate andconcentrated to give methyl(Z)-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetateas white crystals (4.9 mg, yield 64%).

m.p. 158°-161° C.(hexane/ethyl acetate)

EXAMPLE 42

To a suspension of methyl(Z)-2-hydroxyimino-2-(5-methoxycarbonyl-1,2,4-thiadiazol-3-yl)acetate(20.8 mg; 7.99×10⁻² mmol) and silver oxide (55.6 mg; 2.40×10⁻¹ mmol) inanhydrous dimethylformamide (210 μl) was added dropwise t-butylbromoacetate (14.2 μl, 8.79×10⁻² mmol) under stirring at roomtemperature. The mixture was stirred at the same temperature for 5 hoursand then the reaction mixture was directly filtered off through a layerof Celite and washed with ether.

The filtrate was combined with the washings and the mixture wasconcentrated. The crude syrup obtained was purified by columnchromatography (1.5 g Kiesergel, hexane/ethyl acetate=1/1) to givemethyl(Z)-2-t-butoxycarbonylmethyloxyimino-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate(27.5 mg, yield 91.9%).

EXAMPLE 43

To a suspension of methyl(Z)-2-hydroxyimino-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetate(18.2 mg, 6.99×10⁻² mmol), barium oxide (53.6 mg, 3.50×10⁻¹ mmol) andbarium hydroxide octahydrate (11.0 mg, 3.50×10⁻² mmol) indimethylformamide (360 μl) and chloroform (180 μl) was added t-butylbromoacetate (22.6 μl, 1.40×10⁻¹ mmol) under ice-cooing and stirring.The mixture was stirred at the same temperature for 1.5 hours and thenpieces of dry ice were added to the reaction mixture and the insolublematter was filtered through a layer of Celite and the residue was washedand the mixture with ether. The filtrate was combined with the washingswas concentrated. The crude syrup obtained was purified by columnchromatography (Kiesergel 1.5 g, hexane/ethylacetate=1/1) to give methyl(Z)-2-t-butoxycarbonylmethyoxyimino-2-(5-methoxycarbonylamino-1,2,4-thiadiazol-3-yl)acetateas white crystals (15.0 mg, yield 57.2%).

EXAMPLE 44

A suspension of isobutylyl chloride (12.13 g, 0.114 mol) and potassiumthiocyanate (13.7 g, 0.13 mol) in benzene (50 ml) was heated at 80° C.for 8 hours and then 3-aminoisoxazole (2.2 g, 0.026 mol) was addeddropwise thereto under ice-cooling and stirring. The mixture was stirredfor 1 hour at same temperature. Then the reaction mixture was treated inthe same manner as Example 15 to give methyl2-(5-isobutylylamino-1,2,4-thiadiazol-3-yl)acetate 0.4 g.

m.p. 58°-61° C.

NMR δ(CDCl₃): 1.33(6H, -dd), 2.33-3.20(1H,m), 3.70(3H,s), 3.90(2H,3),12.80(1H,bs,NH)

IR(KBr)cm⁻¹ : 1730, 1689.5, 1537.2, 1357.8, 1226.6.

What is claimed is:
 1. A process for production of1,2,4-thiadiazolylacetic acid compound of the formula: ##STR33## whereinR¹ is lower alkyl, and R² is lower alkoxy, phenoxy, benzyloxy, loweralkyl and phenyl optionally substituted by nitro or halogen, whichcomprises reacting an isoxazole of the formula: ##STR34## with anisothiocyanate of the formula:

    SCN--COR.sup.2

at 0°-10° C. in tetrahydrofuran or acetonitrile and subjecting torearrangement reaction in a reaction system without any base to give thecompound (II).